Antistatic film



0d 9, 1945' GQF. NADEAU Erm. 2,386,627

ANTISTATIC FILM med Nov. so, 194s EMULS/0N /suPPoRT cELLuLosE 4ORGANIC Ac/D ESTER coNTA/NING A METALLIC su/ FATE GALE F. NADEAU CLARENCE S.HUNTER ,INVENTORS manna oet. 9, 194s y UNITED `STATES PATE assaszi Nr oFFlcE AN'rrsrA'rIc FILM Gale F. Nadeau andl Clarence S. Hunter, Rochester, N. Y., asslgnors to Eastman Kodak Company, Rochester, N. Y.

Jersey a corporation of lNew Application November 30, 1943, Serial No. 512,366

. 3 Claims.

This invention relates to photographic film and Y particularly toa lm protected against static.

The accumulation of electrical charges on photographic film has been the cause of considerable trouble.' 'Ihese charges are produced by the friction of the film moving over rollers or past the gates' of a camera and are manifested as irregular fogged patterns. in the emulsion of the film after it has been developed. These static effects are particularly noticeable in a film provided with 'a cellulose nitrate support, although with the advent of high speed emulsions practically any iilm support will become suiliciently 1 electrified during manufacture or use so that the dischargesv of stored-up static electricity will affect the sensitive layer. Attempts have been made to overcome static in photographic lms by theapplication of various layers to the film support. These layers have, in general, ,consistedof materials designed to dissipate the electric charges by providing the film with a conducting surface. ture and, therefore, provide a conducting surface lhave frequently been employed. These methods have not proven entirely satisfactory with the Materials which absorb moisnewer high speed emulsions and the absorption of water by the anti-static material is frequently objectionable.

It is, therefore, an object ofthe present invention to provide va novel photographic film backing which will afford static protection for the emulsion. A further object means for coating photographic nlm to reduce itsstatic tendency. Other objects will appear from the followlng'description of our invention.

These objects are -accomplished by incorporating a, metallic sulfate in a layer of a cellulose orside not carrying the sensitive emulsion layer although the anti-static layer may be coated on use is not hygroscoplc; hence the beneficial static results do not depend upon the absorption of moisture by the backing. Furthermore, the surface resistivities of the backed and unbacked films are not greatly different; In'other words the salt does not modify theelectrical resistivity of the nlm. 'I'his is true of both volume and surface resistivities. l

We have found that the incorporation of the metallic sulfate in the backing has little or no static effect until a certain threshold concentration has been reached. Beyond this point the beneficial results increase in proportion to the f concentration of the salt up tothe point# at which is to provide a ganic acidester applied to the nlm support. In

tlie accompanying drawing the single figure is a u sectional view of a film constructed' according to' our invention. l

According to our iuventiona photographic lm support of a cellulose inorganic acid ester such as cellulose nitrate or acellulose organic acid ester, such as cellulose acetate or cellulose acetate butyrate, is coated with a layer of a cellulose organic acid ester containing a suitable amount 1 of a metallic sulfate. Cellulose acetate is preferably used as the carrier for the metallic sulfate ,so

although other cellulose organic acid'esters-may be employed. A solution of the cellulose acetate containing the metallic sulfate is coated o n the nlm support from solvent solution in the conventional'manner. The anti-static layer is preferably on the rear surface of the support or the the salt is no longer compatible with the backing. For aluminum sulfate the amounts, which may be used vary from 1.0% to 40% of the amount of cellulose acetate or other cellulose` organic acid ester in the vfinished coating.

The following examples illustrate the method of applying the antistatic backing according to our invention:

y Example 1 A cellulose acetate butyrate film support is coated with an anti-static layer from the following solution:

. Per-cen Cellulose acetate 3 f Aluminum sulfate (Al:(SO4)s.18H2O) .65 Water 'l 1.5 Methyl alcohol 37.85 Acetone'. 57

This coating is dried and la gelatino-silver halide emulsion layer is then applied to thejopposite side of the support.

The concentration of salt may be varied between about .01% and 2.0% depending on variations in the viscosity f the cellulose acetate. The

concentrations of the other components are not 2 critical'and may vary according to the individual salt and cellulose ester selected.

- Example 2 A cellulose nitrate nlm support is coated by bead application at approximately 10 reet per minute with the following solution:

Our invention will be further illustrated by reference to the accompanying drawing. As shown therein, a support I0 of cellulose ester is coated on one side with an emulsion layer I I and on the opposite side with a layer I2 of cellulose organic acid ester .containing a metallic sulfate.

It will be understood that our invention. is capable of numerous variations and is to -be taken as limited only by the scope o! the appended* claims.

, Per cent Cellulose acetatla 3. l Methyl alcohol 40 l0 Acefnne 56 Aluminum sulfate (Ala(SO4)a.18H'.-O)- l aaeaea'z acid ester of cellulose containing from 1.0% to 40% oi.' aluminum sulfate.

GALE- F. NAIJEAU. CLARENCE s. HUNTER.

thereon a sensi- Y 

